cal cause for their separation. It is
probably the synchronism of the vibrations of one portion of the
molecule with the incident waves, that enables the amplitude of those
vibrations to augment, until the chain which binds the parts of the
molecule together is snapped asunder.

I anticipate wide, if not entire, generality for the fact that a
liquid and its vapour absorb the same rays. A cell of liquid chlorine
would, I imagine, deprive light more effectually of its power of
causing chlorine and hydrogen to combine than any other filter of the
luminous rays. The rays which give chlorine its colour have nothing
to do with this combination, those that are absorbed by the chlorine
being really effective rays. A highly sensitive bulb, containing
chlorine and hydrogen, in the exact proportions necessary for the
formation of hydrochloric acid, was placed at one end of an
experimental tube, the beam of the electric lamp being sent through it
from the other. The bulb did not explode when the tube was filled
with chlorine, while the explosion was violent and immediate when the
tube was filled with air. I anticipate for the liquid chlorine an
action similar to, but still more energetic than, that exhibited by
the gas. If this should prove to be the case, it will favour the view
that chlorine itself is _molecular_ and not _monatomic_.

Production of Sky-blue by the Decomposition of Nitrite of Amyl.

When the quantity of nitrite vapour is considerable, and the light
intense, the chemical action is exceedingly rapid, the particles
precipitated being so large as to whiten the luminous beam. Not so,
however, when a well-mixed and highly attenuated vapour fills the
experimental tube. The effect now to be described was first obtained
when the vapour of the nitrite was derived from a portion of its
liquid which had been accidentally introduced into the passage through
which the dry air flowed into the experimental tube.

In this case, the electric beam traversed the tube for several seconds
before any action was visible. Decomposition then visibly commenced,
and advanced slowly. When the light was very strong, the cloud
appeared of a milky blue. When, on the contrary, the intensity was
moderate, the blue was pure and deep. In Bruecke's important
experiments on the blue of the sky and the morning and evening red,
pure mastic is dissolved in alcohol, and then dropped into water well
stirred. When the proportion of mastic